Simplify the following expression: $p = \dfrac{9}{2x + 9} \div \dfrac{10}{9x}$
Dividing by an expression is the same as multiplying by its inverse. $p = \dfrac{9}{2x + 9} \times \dfrac{9x}{10}$ When multiplying fractions, we multiply the numerators and the denominators. $p = \dfrac{ 9 \times 9x } { (2x + 9) \times 10}$ $p = \dfrac{81x}{20x + 90}$